Developers and manufacturers particularly in this technical application area are confronted by ever increasing requirements regarding the level of performance and pollutant emissions of running combustion engines. This also results in ever increasing demands being placed on the precision, quality and operating mode of the individual components in injection technology, and in this case especially on the fuel injector valves, over the entire life span, e.g., of a vehicle.
Many fuel injection valves currently available are highly complex, electro-mechanical devices which place the most stringent demands on material and production technology. A fuel injection valve of this type may fundamentally comprise the injector body that has an injector shaft with an injector ring chamber, injector needle, closing spring, valve seat and injector holes, as well as an actuating device with an actuator arrangement and transmission mechanics or control hydraulics with a control valve for actuating the injector needle. Electro-magnetic actuating drives or also piezoelectric actuators can be used here as actuators. The injector needle is urged in the idle phase by the closing spring into the valve seat and seals off the injector ring chamber, which is filled with fuel and highly pressurized, from the injector holes.
For the purpose of injecting fuel into the combustion chamber of the internal combustion engine, the injector needle is raised off the valve seat, thus revealing the injector holes, by actuating the actuator and by means of transmission mechanics or control hydraulics. The high pressure fuel is injected through the injector holes directly into the associated combustion chamber. A fuel injection valve of this type is known for example from DE 33 03 470 A1.
DE 33 03 470 A1 discloses an injection nozzle for combustion engines with a pressure chamber in a valve body and an injector needle. The injector needle comprises a sealing cone that lies in a cone-shaped seat of the valve body and seals off the injector holes from the pressure chamber. The cone-shaped seat of the valve body transforms into a blind cut-out described as a well, from which the injector holes extend.
The performance and emission behavior of the internal combustion engine may greatly depend upon the accuracy of the individual fuel injections and upon the geometric conditions in the injector shaft.
The accuracy of the injection quantities may greatly depend upon the available pressure and its constancy in the injector ring chamber and also upon the precision of the activation and the tolerances of the mechanics and in this case in particular of the injector holes. It is a known effect that, as the power density rises and the exhaust gas return rate increases, a greater number of deposits are formed in the injector holes as a result of coking and this has a negative influence on the required accuracy of the fuel injection and thus on the performance and emission behavior.
It is also known that the dead volume, which is referred to below as the compression volume, that is dictated by the construction and formed between the valve seat and the injector hole outlet as a result of the structural design and that is filled with fuel has a negative influence, in particular on the hydrocarbon emissions (HC emissions) of the internal combustion engine. An increase in the compression volume causes higher HC-emissions, as a result of the fuel vaporizing from the injector holes into the combustion chamber following the injection of fuel.